Red-eye artifacts often occur in photography. The occurrence of red-eye artifacts is referred to as “red-eye.” Red-eye artifacts are caused by light entering a subject's eye through the pupil, reflecting off the retina at the back of the eye, and traveling back through the pupil toward the camera lens. The light can originate from a flash used to improve lighting conditions for capturing an image. Red-eye artifacts often appear red- or orange-colored in the captured image. The red or orange color results from the retina absorbing, rather than reflecting, non-reddish components of the light entering the eye. The color that is reflected in a red-eye artifact is determined by the color of the fundus of the eye along with the color of the illuminant (i.e., the light illuminating an image subject). Because the color of the fundus varies from one individual to another, and the color of illuminants varies depending on ambient light, flash equipment, and reflections, the precise color associated with red-eye artifacts can vary substantially across photographs.
Techniques can be used to reduce the occurrence of red-eye artifacts at the time a photograph is taken. For example, the lateral distance between a flash and the lens can be increased. Although light is still reflected by the retina, less light is reflected toward the camera. In addition, pre-flashes can be used to reduce the size of the subject's pupils. Techniques also can be used to reduce the occurrence of red-eye artifacts in images that have been captured. For example, digital processing techniques also exist to remove red-eye artifacts from images in post-capture processing.
Further, images can depict visual information using various color models. A color model can describe how colors are represented, e.g., using one to four values, each corresponding to a color component. For example, in a red-green-blue (RGB) color model, a color can be described using three values—one each for red, green, and blue. Thus, three values can be used to describe the color of each pixel in an RGB image. When an intended interpretation of a color model's components is known, the set of possible colors can be referred to as a color space. For example, the three values associated with an RGB color can be mixed additively to produce a specific color in an RGB color space.